A new solid-state Li ion conductor composed of LiBH 4 and Al 2 O 3 was synthesized by a simple ball-milling process. The element distribution map obtained by transmission electron microscopy demonstrates that the LiBH 4 and Al 2 O 3 are well mixed and form a large interface after ballmilling. The ionic conductivity of the mixture reaches as high as 2 × 10 −4 S cm −1 at room temperature when the volume fraction of Al 2 O 3 is approximately 44%. The ionic conductivity of the interface between LiBH 4 and Al 2 O 3 was extracted by using a continuum percolation model, which turns out to be about 10 −3 S cm −1 at room temperature, being 10 5 times higher than that of pure LiBH 4 . This remarkable rise in conductivity is accompanied by the lowered activation energy for the Li ion conduction in the mixture, indicating that the interface layer facilitates Li ion conduction. Near-edge X-ray absorption fine structure analysis reveals the presence of B− O bondings in the mixture, which was not detected by X-ray diffraction. This disruption of the chemical bondings at the interface may allow an increase in carrier concentration and/or mobility thereby resulting in the pronounced enhancement in conductivity. This result provides a guideline for designing fast Li ion conductor through interface engineering.

The evaluation test of various thin film contact materials for reliable radio frequency (RF) microelectromechanical systems (MEMS) switches is presented. Given that two of the most important performance criteria of RF MEMS switches are a low contact resistance and high reliability, the purpose of this study is to search for feasible contact materials and combinations by measuring the contact resistance and hot switching reliability under high current condition. We selected gold, platinum, and iridium for the contact materials and compared the contact resistance and failure point for various similar or dissimilar contacts; Au/Au, Pt/Pt, Ir/Ir, Au/Pt, and Au/Ir using a contact measurement apparatus. Also, we investigated the insertion loss and power handling capability of Au/Au and Au/Ir in the RF MEMS switches. From these studies, it was found that dissimilar contacts such as Au/Pt or Au/Ir are an effective means of enhancing the reliability for high power RF MEMS switches. This evaluation method represents an important step toward the development of reliable metal contacts.

One of the important mechanical properties of cryogenic temperature structure material is fracture toughness. Research on normalization of fracture toughness test method is becoming very important issue with development of cryogenic structural elements. Specially, mechanical properties estimation by each micro-structure of welding department is important because it can cause unstable fracture when use under cryogenic environment in case of welding department. In this study, fracture toughness estimation test was carried out to unloading compliance method and sensitization heat-tread minimized test specimen at liquid nitrogen (77K), liquid helium (4K), 293K temperature to STS-316L base metal and weld metal.

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